Wireless LANs and PANs 01204325: Data Communication and Computer Networks Asst. Prof. Chaiporn Jaikaeo, Ph.D. [email protected] cpj.

Wireless LANs and PANs

01204325: Data Communication and Computer Networks

Asst. Prof. Chaiporn Jaikaeo, [email protected]

http://www.cpe.ku.ac.th/~cpjComputer Engineering Department

Kasetsart University, Bangkok, ThailandAdapted from lecture slides by Behrouz A. Forouzan© The McGraw-Hill Companies, Inc. All rights reservedMaterials taken from lecture slides by Karl and Willig

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Outline Electromagnetic spectrum and ISM

bands IEEE 802.11 (Wi-Fi) Bluetooth IEEE 802.15.4

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Electromagnetic Spectrum

Government regulations make specific ranges of the electromagnetic spectrum available for communication

A license is required to operate transmission equipment in some parts of the spectrum Some parts are unlicensed

RF range

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ISM Bands Industrial, Scientific, and Medical

frequency bands Can operate without FCC licenses Tx output power 1 watt Eliminate cost and time consuming for

licenses

26MHz

902MHz

928MHz

915 MHz*

100 MHz

2.40GHz

2.50GHz

2.45 GHz

150 MHz

5.725GHz

5.875GHz

5.8 GHz

* Region 2 only

Wireless LANs:IEEE 802.11 (Wi-Fi)

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IEEE 802.11 IEEE Standard for Wireless LANs Covers both physical and data link

layers

Wi-Fi Access points Wi-Fi Router

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WLAN Architectures Basic Service Set (BSS) Extended Service Set (ESS)

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Basic Service Set (BSS)

(Ad hoc mode) (Infrastructure mode)

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Extended Service Set (ESS)

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IEEE 802.11 Physical Layer

IEEE 802.11 MAC

802.11a 802.11b 802.11g 802.11n

6-54 Mbps5 GHzOFDM

1-11 Mbps2.4 GHz

DSSS

6-54 Mbps2.4 GHzOFDMDSSS

7.2-150 Mbps

2.4, 5 GHzOFDM

802.11

1-2 Mbps2.4 GHz

FHSSDSSS

IR

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IEEE 802.11b/g Channels

See http://en.wikipedia.org/wiki/List_of_WLAN_channels

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IEEE 802.11 MAC Layer

PCF – Point Coordination Function (controlled access)DCF – Distributed Coordination Function (random access)

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CSMA/CA Used by 802.11 Basic CSMA/CA not enough

"Hidden Terminal Problem"

A B C

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CSMA/CA With RTS/CTS

RTS

CTS

Data

ACK

A B C D

NAVNAV

NAV Network Allocation Vector

(Virtual Carrier Sensing)

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IEEE 802.11 and Wi-Fi IEEE 802.11 provides most of the

standards A group of vendors who build

wireless equipment formed the Wi-Fi Alliance A non-profit organization that tests

and certifies wireless equipment using the 802.11 standards

Wireless PANs: Bluetooth

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Bluetooth Standard Wireless Personal Area Network

technology Designed for connecting devices with

different functionalities: Telephone, mouse, keyboard, camera,

etc. Standard IEEE 802.15.1

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Bluetooth Piconet

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Bluetooth Scatternet

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Bluetooth Layers

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Bluetooth Communication Single slave

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Bluetooth Communication Multiple slaves

Low-Rate Wireless PANs:

IEEE 802.15.4

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IEEE 802.15.4 IEEE standard for Low-Rate

WPAN (LR-WPAN) applications Low-to-medium bit rates Moderate delays without too

strict requirements Low cost, low energy

consumption Applications

Home automation and security systems

Smart metering Wireless data collection

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868MHz (20 kbps)

2.4 GHz

868.3 MHz

Channel 0 Channels 1-10

Channels 11-26

2.4835 GHz

928 MHz902 MHz

5 MHz

2 MHz

2.4 GHz PHY

IEEE 802.15.4 Physical Operating frequency bands

915 MHz (40 kbps)

2.4 GHz (250 kbps)

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IEEE 802.15.4 MAC Single channel at any one time Combines contention-based and

schedule-based schemes Asymmetric: nodes can assume

different roles

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IEEE 802.15.4 Devices Full function device (FFD)

Any topology Network coordinator capable Talks to any other device

Reduced function device (RFD) Limited to star topology Cannot become a network coordinator Talks only to a network coordinator Very simple implementation

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IEEE 802.15.4 Topologies